Nitrite photometrical determination

In this development of a flow injection method for the determination of nitrate andnitrite, Anderson [168] chose the Shinn [155] method to reduce nitrate and nitrite because of its high sensitivity and relative freedom from interferences. Anderson [168] used flow injection in the photometric determination of nitrite and nitrate with sulfanilamide and N-( 1-naphthyl) ethylenediamine as reagents, as discussed next. The detection limit is 0.05 xm for nitrite and 0.1 xm for nitrate at a total sample volume of 200 iL. Up to 30 samples can be analysed per hour with relative precision of about 1%. 

Peak smoothing is also an option, as demonstrated in the spectro-photometric determination of nitrate and nitrite [93]. The signals recorded for the blank and the sample were processed by applying a simple algorithm, allowing the blank signal to be subtracted. Analytical repeatability, however, was impaired due to the error propagation effects involved. 

S. Nakashima, M. Yagi, M. Zenki, A. Takahashi, and K. Toei, Spectro-photometric Determination of Nitrite in Natural Waters by Flow Injection Analysis. Anal. Chim. Acta, 155 (1983) 263. 

The standard-addition method can take several forms." The one most often chosen for photometric or spectrophotometric analyses, and the one that was discussed in some detail in Section ID-.1, involves adding one or more increments of a standard solution to sample aliquots. Each solution is then diluted to a fixed volume before measuring its absorbance, lix-ample 14-1 illustrates a spreadsheet approach to the multiple-additions method for the photometric determination of nitrite. 

M.A. Feres, B.F. Reis, A downsized flow set up based on multicommutation for the sequential photometric determination of iron(II)/iron(III) and nitrite/nitrate in surface water, Talanta 68 (2005) 422-428. 

Several tests that could not be carried out in the field were completed in the laboratory within five hours after the samples were collected. These included chemical oxygen demand (COD), which was determined photometrically after oxidation of the oombustible organic material in chromate sulfuric add in the presence of silver sulfate. The nitrate concentration was calculated from the nitrite concentration determined photometrically employing the Griess Reaction after the reduction of the nitrate to nitrite by metallic cadmium. The nitrite-N concentration determined in the field was subtracted 6om the result to calculate the nitrate-N content of the water, which was then converted to the nitrate concentration by multiplication. Fluoride was determined photometrically based on the decoloration of Spadns reagent. 

Nitrites at concentrations of 0.002-0.6 mg F are determined photometrically with sulphanilic acid and a-naphthylamine. 

The nitrogen contained in organic substances in water is converted to ammonium ions by KjeldahEs decomposition method. The ammonium ions are distilled from alkaline solution as ammonia, collected in boric acid solution and determined acidimetrically or photometrically in the receiver. Ammonium ions originally contained in the sample are separated, identified and deducted, or separated off by distillation before carrying out the Kjeldahl decomposition. Nitrite and nitrate are volatilized by H2SO4 in the... 

Nitrate and nitrite The nitrate and nitrite content of cheeses that have been treated with these salts can be determined by reduction with cadmium followed by reaction with sulfonamide and N-l,nap-hthylethylenediamine hydrochloride. This produces a colored compound that can be quantified spectro-photometrically. 

Gas chromatography Acesulfame-K, aspartame, cyclamate, saccharin, and stevioside are determined by gas chromatography, but the main drawback of this technique is that a derivatization is required. Acesulfame-K is methylated with ethereal diazomethane, aspartame is converted into its N- 2-methylpropoxycarbonyl) methyl ester derivative, menthol and isobutyl chloroformate are used to convert aspartame to 3-[(isobutoxycarbonyl)amino]-4-[[a-(methoxycarbonyl)phenethyl]amino]-4-oxobutyric acid, cyclamate is determined as cyclohexene resulting from the reaction with nitrite, saccharin is converted to N-methylsaccharin, and stevioside is hydrolyzed. Detection is carried out utilizing flame-ionization, flame-photometric electron-capture detectors or nitrogen-phosphorus detection. 

Nitrite may be determined through the reaction with sulfanilamide and N-(l-naphthyl)ethylenedia-mine in acidic solution. The lower limit of detection of this method is 30pgl nitrite. Because of its simplicity and reliability, photometric detection is still preferred. 

Phosphate is mostly determined photometrically through the reaction with ammonium heptamolyb-date in acidic medium in the presence of potassium antimonyl tartrate as a catalyst. 12-Molybdophos-phoric acid is formed that upon reduction with, for example, ascorbic acid has a blue color. The lower limit of detection is lOpgl. Chromium(VI), nitrite, and high concentrations of chloride and iron interfere. The lower recoveries caused by iron are eliminated by addition of hydrogensulfite. 

A method claimed to be applicable for a minimum detectable activity of less than 0.05 pCI/i of sample at the time of counting has been reported (86). Carrier was mixed with the milk sample and the mixture was heated to about 75°. Iodide was collected on an anion exchange resin (resin not specified) and then eluted as lodate by means of hypochlorite. lodate was converted to free Iodine by treatment with hydroxylamlne hydrochloride and sodium nitrite. An l2"I cycle was performed and the Iodine extracted Into toluene in which medium It was determined photometrically for chemical yield. 2-Methyl butene was added to the toluene solution and the liquid sample was mixed with a toluene-based liquid scintillation counting solution and 8-gated y coincidence counting was carried out. 

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